SharePoint Vulnerability Exploited in the Wild, Puts Users at Risk
A recently patched SharePoint vulnerability is being actively exploited by attackers, just days after a proof-of-concept (PoC) exploit was released. The weakness, tracked as CVE-2026-55040, allows an unauthenticated attacker to bypass security features and access sensitive data on a SharePoint site.
Microsoft had fixed the issue with its July Patch Tuesday updates, describing it as a weak authentication problem that could be exploited by attackers over a network. “Exploiting this vulnerability could allow an attacker to disclose files and modify data,” Microsoft warned at the time. “In a network-based attack, an unauthenticated attacker could bypass authentication and make an anonymous connection.”
The rapid exploitation of CVE-2026-55040 is particularly concerning because it occurred shortly after Rapid7 disclosed technical details about the vulnerability on August 11. The security firm provided a PoC script to demonstrate how the exploit works, which was quickly picked up by attackers.
According to threat intelligence firm Defuse, its honeypots have recorded exploitation attempts targeting CVE-2026-55040, with attacks leveraging the PoC released by Rapid7. This surge in exploitation is not isolated – Microsoft’s advisory for the vulnerability still doesn’t mention any known exploits, but it’s common for the company to update its advisories only after attacks are confirmed.
The recent wave of SharePoint vulnerabilities being exploited has caught the attention of CISA, which recently urged organizations to ensure their SharePoint instances are up-to-date and protected. The agency warned that CVE-2026-55040 could be exploited in the wild, but it’s still unclear who is behind these attacks.
This vulnerability is just one of five SharePoint flaws whose exploitation has been spotted this summer, including CVE-2026-50522, CVE-2026-58644, CVE-2026-56164, and CVE-2026-45659. However, there’s no public information on who is behind these attacks.
As the number of exploited vulnerabilities continues to rise, it’s essential for organizations to stay vigilant about their SharePoint security. This means keeping software up-to-date, monitoring network activity closely, and implementing robust security measures to prevent unauthorized access.
To protect yourself from falling victim to similar exploits in the future, ensure that your SharePoint instance is patched with the latest updates, monitor your network activity regularly, and implement strong authentication mechanisms to prevent unauthorized access. Additionally, keep an eye on official advisories and security alerts issued by trusted sources like Microsoft and CISA to stay informed about emerging threats and vulnerabilities.
Source: SecurityWeek — 2026-08-12